In an LTE (Long Term Evolution) scheme, a mobile station UE is configured to transmit, to a radio base station eNB, PHR (Power headroom report) including Power headroom through PUSCH (Physical Uplink Shared Channel, uplink shared channel) according to a predetermined transmission trigger.
Furthermore, the Power headroom indicates information on the difference between an estimated value of desired transmission power on the PUSCH for the mobile station UE and a maximum transmission power. In addition, the desired transmission power on the PUSCH is configured to be calculated on the basis of a path loss (Pathloss) estimated from a downlink.
In order to actually estimate the path loss from the downlink, the mobile station UE is configured to calculate the path loss by the difference between a transmission power (Resource Element unit) of a downlink common pilot signal (a cell-specific reference signal) in the radio base station eNB and a received power (Resource Element unit) of the downlink common pilot signal in the mobile station UE.
The radio base station eNB is configured to detect the amount of remaining transmission power available in the mobile station UE on the basis of the PHR, and to assign an uplink resource to the mobile station UE.
In an LTE-Advanced scheme which is a next generation of the LTE scheme, a mobile station UE is configured to be able to perform a CA (Carrier Aggregation) communication with a radio base station eNB by using a plurality of DL CCs (Downlink Component Carriers, downlink carriers) and a plurality of UL CCs (Uplink Component Carriers, uplink carriers), each of which has a different carrier frequency.
Furthermore, in the CA communication, in a case in which new DL CC was added or a case in which an inactive state of DL CC was changed to an active state, it is not possible for the radio base station eNB to detect available transmission power on the UL CC according to Power headroom until the Power headroom calculated on the basis of a path loss estimated from the DL CC is received, and thus there is a problem that it is not possible to perform appropriate scheduling on the UL CC.
Specifically, there may be a difference in path loss on the CCs, and thus it has been considered to notify it to the mobile station UE from the radio base station eNB, which DL CC is used for estimating the path loss, which is used by the mobile station UE in order to control transmission power on UL CCs used in a CA communication with the mobile station UE.
For example, on the basis of the configuration of CC in FIG. 1, when the radio base station eNB performs the CA communication with the mobile station UE, UL PCC and DL PCC are in the same path loss environment, and UL SCC#1, UL SCC#2, DL SCC#1, and DL SCC#2 (the UL PCC and the DL PCC are different from each other) are in the same path loss environment, the radio base station eNB notifies the mobile station UE of the fact that the path loss used in order to control transmission power on the UL PCC is to be estimated from the DL PCC, and the path loss used in order to control transmission power on the UL SCC#1 and the UL SCC#2 is to be estimated from the DL SCC#1 or the DL SCC#2. When there is a difference in path loss on the CCs, in order to allow the radio base station eNB to appropriately perform uplink resource assignment on each UL CC, it is necessary for the mobile station UE to transmit independent Power Headroom to the radio base station eNB, wherein the independent Power Headroom correspond to the number of DL CCs notified to be used to estimate the path loss from the radio base station eNB.
In the aforementioned example, it is necessary for the mobile station UE to transmit, to the radio base station eNB, Power Headroom obtained from desired transmission power of PUSCH on the UL PCC calculated on the basis of the path loss estimated from the DL PCC, and Power Headroom obtained from desired transmission power of PUSCH on the UL SCC#1 and the UL SCC#2 calculated on the basis of the path loss estimated from the DL SCC#1 or the DL SCC#2.
Then, the radio base station eNB performs uplink resource assignment on the UL PCC on the basis of the Power Headroom obtained from the desired transmission power of the PUSCH on the UL PCC calculated on the basis of the path loss estimated by the mobile station UE from the DL PCC, and performs uplink resource assignment on the UL SCC#1 and the UL SCC#2 on the basis of the Power Headroom obtained from the desired transmission power of the PUSCH on the UL SCC#1 and the UL SCC#2 calculated on the basis of the path loss estimated by the mobile station from the DL SCC#1 or the DL SCC#2.
However, in the CA communication, in the case in which new DL CC was added or the case in which the inactive state of DL CC was changed to the active state, it is not possible for the radio base station eNB to detect the available transmission power on the UL CC according to the Power headroom until the Power headroom calculated on the basis of a path loss on the DL CC is received, and thus there is a problem that it is not possible to perform appropriate scheduling on the UL CC.
Therefore, the present invention has been achieved in view of the above-described problems, and an object thereof is to provide a mobile communication method and a mobile station, in a CA communication, in a case in which new DL CC was added or a case in which an inactive state of DL CC was changed to an active state, by which it is possible to quickly perform appropriate scheduling on UL CC according to Power headroom calculated on the basis of a path loss estimated from the DL CC.